Stroboscope



Sept. 10, 1929. c. A. NICKLE 1,728,003

STROBOSCOPE Filed May 19, 1927 Inventor- CliFFord A. Nickle,

y M His Afitorneg Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

CLIFFORD A. NIGKLE, F SOHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEC-TRIO COMPANY, A CORPORATION OF NEW YORK.

STROBOSCOPE.

Application filed May 19, 1927. Serial No. 192,767.

My invention relates to electrical apparatus and its principal object isto provide electrical stroboscopic apparatus which has no moving partsexcept the object under stroboscopic observation. A further ob ect ofthe invention is to provide an electric stroboscopic light producingmeans which gives exceptionally short but bright stroboscopicillumination which enables its use for observing exceptionally highspeed phenomena.

In the preferred embodiment of my invention I provide an alternatingcurrent transformer. The transformer core is designed to permitsaturation over a substantial portion of the flux wave therein. Thetransformer carries a primary energizing winding and a secondary windingfor energizing a stroboscopic lamp. The action is such as to produceintermittent sharp current impulses in the secondary circuit andcorrespondingly intermittent sharp illuminations of the lamp. Thefeatures of my invention which are believed to be novel and patentablewill be pointed out in the claims appended hereto.

For a better understanding of the invention reference is made in thefollowing description tothe accompanying drawing in which Fig. 1represents the physical embodiment of the invention and one of its uses,and Fig. 2

represents approximate wave shapes of primary current and secondaryvoltage of the transformer.

Referring to the drawing, 10 represents the core of a transformer, 11its primary winding, and 12 its secondary winding. The transformer corehas a reduced portion or portions 13 which are designed to becomesaturated at a low percentage of the normal transformer flux. Connectedin the secondary circuit is one or more stroboscopic lamp devices. Forthis purpose I prefer to employ neon tubes or lamps one of which isshown at 14, A protective reactance 15 is preferably included in theprimary circuit of the transformer for reducing the primary current.This is desirable because the transformer itself will have low reactanceover the greater portion of a current cycle because of the saturatedcondition of the sections 13 of its core. lVhen this apparatus isenergized with an alternating current of approximately a sine wavevoltage, we may represent the primary current by curve I, Fig. 2. Thiscurve will usually be distorted somewhat from that of a true sine waveshape in the region where the transformer core becomes saturated becauseof the varying reactance in the primary circuit but so far as theinvention is concerned such distortion is immaterial. When the portions13 are saturated, as from point A to point B of the primary currentwave, the reactance of winding 11 will be low and practically all of theprimary voltage will appear across 15. \Vhen the portions 13 are belowsaturation as-from points B to C of the current Wave the full reactanceof the transformer appears and the primary voltage is divided across 15and coil 11, and the voltage across the primary coil will have somecertain ratio to the line voltage. By transformer action, a proportionalvoltage is induced in the secondary winding 12; Thus, from points B to Gof the primary current wave the action of the transformer is like thatof an ordinary transformer and from points A to B the series reactance15 keeps the primary current from increasing to undesirable values.

We may represent the secondary voltage which appears across thesecondary Winding 12 and lamp 14 by the curve V. From A to B when thereduced sections of the core are saturated, the leakage flux of thetransformer is excessive and the rate of change of the transformer fluxis the least. Con sequently the rate of change of flux threading thesecondary winding D is very low and the secondary voltage iscorrespondingly loW. As the primary current passes through zero the rateof change of the transformer flux is a maximum and the sections areunsaturated at this time so that from B to C the flux threading thesecondary Winding has a very greatly magnified rate of change and as aresult the secondary voltage rises in a sharp peak of very shortduration as represented at D. This peak occurs at every half cycle andis the voltage utilized to illuminate the lamp 1 1 stroboscopically. Thelamp 14 is selected with the design of the apparatus so that forvoltages such as are present from points A to B no illumination isproduced, but for voltages occurring over the short range from B to C,intensive illumination is produced. The neon lamp is especially suitedfor this pur pose since its characteristics are somewhat like that of acondenser and the effective illumination seems to be dependent more onthe rate of change of voltage than on the magnitude. For a 110 voltprimary source of supply the transformer is preferably designed to stepup the voltage and has many more turns in the secondary than in theprimary. Best results, with a neon tube, are obtained with a relativehigh peak voltage at D. For example, this may be as high as 5000 volts.As a result of such an arrangement, sharp intensive flashes of light areproduced, the periodicity of which depend upon the frequency of supply,which of course may be varied to suit the rate-of movement of the objectunder stroboscopic observation.

Very rapidly moving objects may belamp.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodimentthereof;but I desire to have it understood that the apparatus shown anddescribed is only illustrative and that the invention may be carried outby other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. Stroboscopic apparatus comprising a neon lamp, an alternating currentsource of supply, and means connected between said source and lamp forchanging a substantially sine wave voltage to sharp intermittent peal;voltage impulses.

2..Stroboscopic apparatus comprising a neon lamp, an alternating currentsource, a step-up transformer connected between said source and lamp,said transformer having a core designed to become saturated oversubstantial portions of the flux wave of said transformer.

3. In combination a neon lamp, a transformer for energizing said lamphaving primary and secondary windings wound on a core member having areduced'section between said windings designed to operate above andbelow saturation over different portions of the flux wave of saidtransformer, and a means connected in series with the primary winding ofsaid transformer to limit the current therein.

4. Stroboscopic apparatus comprising a neon lamp, an alternating currentsource, a transformer connected between said source and lamp, saidtransformer having a core designed to become saturated over asubstantial portion of the flux wave of said transformer, and areactance connected in series on the primary side of said transformerfor limiting the supply current thereto.

Stroboscopic apparatus comprising an alternating current transformerhaving a core and primary and secondary windings thereon, said corehaving a reduced crosssection so as to operate above saturation for allbut a short portion of the alternating flux wave therein, and anelectric lamp energized by the secondary winding of said transformer,said lamp being effectively energized only by the secondary voltages ofsaid transformer produced during the time the reduced portion of saidcore is unsaturated.

in witness whereof, I have hereunto set 'my hand this 18th day of May,1927.

CLIFFORD A. NICKLE.

